Rust inhibiting lubrication oil additives

ABSTRACT

THE REACTION PRODUCT OF HYDROCARBYL-SUBSTITUTED SUCCINIC ACID WITH 5- AND 6-MEMBERED RING N-HETEROCYCLIC COMPOUNDS IS FOUND TO BE AN EFFECTIVE RUST INHIBITOR. THE HYDROCARBYL RADICAL CONTAINS LESS THAN 30 CARBON ATOMS. THE N-HETEROCYCLES ARE EXEMPLIFIED BY PYRROLIDINE, 2-AMINOTHIAZOLE, PIPERIDINE, 2-AMINOPYRIDINE AND 2-AMINO-4METHYL PYRIDINE.

United States Patent O 3,785,981 RUST INHLBITING LUBRICATION OIL ADDITIVES Bruce W. Hotten, Orinda, Calif., assignor to Chevron Research Company, San Francisco, Calif. No Drawing. Filed Sept. 29, 1971, Ser. No. 184,740 Int. C1. C10!!! 1/32 US. Cl. 252-515 A 6 Claims ABSTRACT OF THE DISCLOSURE The reaction product of hydrocarbyl-substituted succinic acid with 5- and 6-membered ring N-heterocycle compounds is found to be an effective rust inhibitor. The hydrocarbyl radical contains less than 30 carbon atoms. The N-heterocycles are exemplified by pyrrolidine, 2-aminothiazole, piperidine, 2-aminopyridine and 2-amino-4- methyl pyridine.

BACKGROUND OF THE INVENTION Field of the invention The rusting of ferrous metal surfaces is a common problem in the field of lubrication. The problem occurs with serious consequences in internal combustion engines and turbines where operating conditions impose severe rust inhibitory requirements on lubricants. As a consequence, it is necessary to compound with such lubricants a certain amount of antirust additive.

The rusting problem is extremely severe when water or other materials are present in the lubricating oil which promote or enhance rusting. Two important properties of a rust inhibitor for lubricating oil are the ability to inhibit the formation of rust and the abilit to resist the formation of stable emulsions in such lubricants. Specific laboratory tests have been devised to measure each of these properties. The acceptance of any modern rust inhibitor for lubricating oils is predicated to a large extent upon the results of these tests.

Description of the prior art Many materials have been proposed as addition agents to impart antirust properties to lubricating oils which are ineffective under the severe operating conditions encountered in turbines and marine engines. Proposed inhibitors include those containing 2 or more carboxylic acid groups, U.S. Pats. 2,133,734, 2,962,443, and 3,121,057. Amine derivatives of succinic acid have also been proposed, U.S. Pats. 2,490,744, 2,625,511, 3,272,746, 3,399,141, 3,427,- 245, and 3,458,530. Alkylthio-acetic acids, substituted imidazolines and amine phosphates are among the variety of other compounds which have been proposed as rust inhibitors, U.S. Pats. 2,884,379, 3,158,576, 3,088,910, 3,116,252, 2,371,851, and 2,403,725-6 SUMMARY OF THE INVENTION Hz-C "ice

in which R is an aliphatic hydrocarbyl radical having at least 8 carbon atoms and less than about 30 carbon atoms.

The products obtainable from the reaction of the hydrocarbyl-substituted succinic anhydride with the N-heterocycles of the present invention are of the following general formulas. When the heterocycle is amino-substituted, the composition is of the general formula ll H 0 wherein R is a hydrocarbyl radical of from 8 to 30 carbon atoms and R is an N-heterocycle radical containing at least 1 nitrogen atom. The heterocycle from which R is derived is a 5- or 6-membered ring. The heterocycle can be hydrocarbyl-substituted.

In other compositions which have found use within the scope of the present invention, the reaction product of the hydrocarbyl-substituted succinic anhydride and the N-heterocycle is of the general formula wherein R is a hydrocarbyl radical of from 8 to 30 carbon atoms and R is a N-heterocyclic radical derived from a saturated 5- or 6-membered ring N-heterocycle containing 1 nitrogen atom and said nitrogen atom is directly bonded to the succinyl radical.

The hydrocarbyl-substituted succinic anhydride and the N-heterocycle are reacted in a mole ratio of about 1:1, either exothermically starting at room temperature, or heated to about C. Analysis of the product shows that a nitrogen atom is directly attached to the succinyl radical. The product available from this reaction has the ability to impart valuable rust inhibition properties to a lubricant without the formation of emulsions. For example, the product is markedly superior in rust inhibition to the reaction product of hydrocarbyl-substituted succinic anhydride with aniline, which is a homocyclic aromatic amine, or imidazole, which contains 2 nitrogen atoms. Other heterocyclic amines such as the imidazolines do not meet the critical requirements for turbine oils, for example, they give rise to heavy rusting or have poor demulsibility. On the other hand, the products of the present invention are effective for the purposes for which they are intended in small amounts.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the hydrocarbyl-substituted succinic acid or anhydride reactant of the present invention, the hydrocarbyl is of about 8 to about 50 carbon atoms. (A hydrocarbyl is a monovalent organic radical composed solely of carbon and hydrogen, which may be aliphatic, alicyclic or aromatic, or combinations thereof, e.g., aralkyl.) Usually, the hydrocarbyl will be alkyl or alkenyl; the hydrocarbyl may be derived from petroleum and its nature depends to a large extent on the reaction by which the hydrocarbyl-substituted succinic acid is prepared. This reaction usually involves the addition of an olefin to maleic acid or anhydride, in which case the double bond of the maleic acid anhydride becomes saturated and there remains in the hydrocarbyl at least one olefinic double bond. If it is desired, the olefinic bonds may be saturated by hydrogenation.

In one embodiment of this invention an alpha-olefin, such as those obtained from cracking wax (cracked wax olefins), is reacted with maleic anhydride to form an 3 alkenyl succinic anhydride. This product may then be hydrogenated to form the alkyl succinic anhydride. However, in most instances there would be little advantage if any in the alkyl over the alkenyl succinic anhydride. The methods of reacting an olefin with maleic anhydride are well known in the art and do not require exemplification here. Illustrative of various alpha-olefins which may find use are l-decene, l-undecene, l-dodecene, l-tridecene, 1- tetradecene, l-pentadecene, l-hexadecene, l-heptadecene, l-octadecene, l-nonadecene, l-eicosene, l-heneicosene, etc.

When the addition reaction with maleic anhydride is utilized, or otherwise, it is often desirable to use as the olefinic hydrocarbon reactant a low molecular weight polymer of a C -C olefin (i.e., an oligomer of C -C olefin). Such oligomers are represented by tetrapropylene, triisobutylene, tetraisobutylene, etc. Such oligomers are mono-olefins of a straight or branched chain structure.

A particularly preferred method of preparing the reaction product of this invention is the addition of the oligomer tetrapropylene to maleic acid anhydride followed by reaction of the addition product with an N- heterocycle.

In the synthesis of the products of the present invention, the hydrocarbyl-substituted succinic anhydride is mixed with the N-heterocycle in a mole ratio of about 1:1. The reaction proceeds either exothermically or with the addition of heat to about 100 C.

After reaction for several hours, the product is separated by the usual means. Infrared analysis and titration of the product were utilized to establish its chemical structure.

The N-heterocycle reactants of the present invention are fiveand six-membered heterocyclic compounds, which contain at least one nitrogen atom in the ring itself when amino-substituted and no more than one nitrogen atom in the ring when not aminosubstituted. In general, when the N-hetero-cycle is amino-substituted, the ring itself is unsaturated, i.e., there are no hydrogens attached to the nitrogen atom in the ring.

In particular embodiments of this invention the heterocyclic ring is substituted with C -C aliphatic groups, amino-groups, or other organic aliphatic substituents. These N-heterocyclic compounds are well known, commercially available chemicals, exemplified by pyrrolidine, Z-aminopyridine, and 2-amino-4-methyl pyridine.

The N-heterocycle, to be useful, must be sufficiently reactive towards the hydrocarbyl-substituted succinic acid or anhydride to carry the reaction forward at applied temperatures below about 200 C., e.g., pyrrole is insufficiently reactive in this regard to be of use. Imidazole is weakly (or slowly) reactive at 100 C., but yields a reaction product of little rust inhibitory value, which is markedly inferior to, for example, pyrrolidine.

The following examples illustrate the reaction conditions, reactants and products of the present invention, but are offered for purposes of illustration rather than limitation.

I EXAMPLE 1 p 7.1 g. (approximately 0.1 mole) of pyrrolidine was mixed with 27 g. (approximately 0.1 mole) of tetrapropenyl succinic anhydride (TPSA) and stirred for about 1 hour at approximately 100 C. The reaction was exothermic and infrared analysis of the product showed the presence of amide.

EXAMPLE 2 10 g. of 2-aminothiaz0le was mixed with 27 g. of TPSA at 100 C. for approximately 1 hour. Infrared analysis of the product shows the presence of amide and acid.

EXAMPLE 3 8.5 g. of piperidine was mixed with 27 g. of TPSA and stirred for about 1 hour at approximately 100 C. The reaction was exothermic and infrared analysis of the product showed the presence of amide and acid.

EXAMPLE 4 9.4 g. of Z-amino-pyridine was mixed with 27 g. of

V TPSA and heated for about 1 hour at approximately 100 C. The acid number of the product was 165 mg. KOH/g. (calculated 154), and the base number was 1 mg. KOH/g. (calculated 163).

EXAMPLE 5 11 g. of 2-amino-4-methylpyridine was mixed with. 27 g. of TPSA and stirred for about 1 hour. The reaction was exothermic to C. The base number of the product was 149 mg. KOH/g. (calculated 146), and the acid number was mg. KOH/ g. (calculated 148).

EXAMPLE 6 9.3 g. of anline and 27 g. of TPSA were stirred for 1 hour. The reaction was exothermic and infrared analysis of the product showed the presence of acid and amide.

The products of this invention were tested under a variety of severe conditions to demonstrate their excellence in inhibiting rust formation.

The tests reported are the turbine oil test, ASTM D 665 and the Emulsibili ty Test ASTM D 1401. The latter test demonstrates the ability of oil and water to separate from each other. Since it is essential that the oil and water separate at a reasonable rate in a turbine, the effect of any additives upon the separation is essential to a determination of their eificacy. The turbine oil test is a rust test which uses both distilled and synthetic sea water on a standard carbon steel specimen. The following table indicates results obtained both as to emulsibility and rusting indistilled water as well as synthetic sea Water. The sample used 0.1 weight percent of the reaction product of hydrocarbylsubstituted succinic anhydride and an N- heterocycle in a base oil comprising a heavy turbine oil of viscosity 460 SSU at 100 F. and 61 SSU at 210 F.

TABLE Rust test 1 ASTM D 665 Emulsion test Composition 7 Distilled H O Sea. Water ASTM D 1401 Base nil 100% 100% N -heterocycle Hydrocarbyl 8 Pyrrolidine Tetrapropenyl No rust No emulsion. Z-aminothiazole. -do Do. Pyridine d 2 spots 1% rust D0. 2-am nopyridine .-do N0 rust Light 111 t Do. 2-am1no-4-methylpyridi do 0 rust. Do. Aniline 50% rust... Imidazole .do do 1 Results reported as percent rust on carbon steel spindle.

2 Composition is 0.1 weight percent of additive in base oil.

a The hydrocarbyl radical of the hydrocarbyl-substituted succinic anhydride, 4 An line is not a heterocyclie compound, but aminobenzene.

The compositions of this invention are shown to permit rapid separation between the oil and Water, while providing excellent rust protection. The reaction products of tetrapropenyl succinic anhydride with imidazole and aniline are included for purposes of comparison. The aniline and imidazole reaction products with hydrocarbylsubstituted alkenyl succinic anhydrides are considered inoperative for the stringent requirements of the present invention. It is also interesting to compare the products of the present invention with hydrocarbyl-substituted imidazolines. For example, the ethenolic-substituted imidazole having a hydrocarbyl substituent which is derived from coconut oil acids gives heavy rusting in the ASTM D 665 sea Water test, while on the other hand, when the hydrocarbyl substituent is derived from tallow wax, 40 ml. of emulsion is obtained in the ASTM D 1401 emulsion test. Consequently, a small class of heterocyclic amine derivatives with hydrocarbyl substituents satisfies the stringent requirements of the present invention.

The tabulated results demonstrate the extraordinary capability of the composition of this invention in protecting ferrous metals from rusting. Moreover, While providing corrosion protection in the turbine oil test, they are also capable of passing the Emulsibility Test, essential to their usefulness in turbines.

The additives of the present invention will be present in lubricating oils and greases in concentrations of from 0.01 to 5 percent by weight, and preferably 0.05 to 3 percent by weight. In addition, these lubricating compositions may also contain other lubricating oil and grease additives such as oiliness agents, extreme pressure agents, additional rust inhibitors, oxidation inhibitors, corrosion inhibitors, viscosity index improving agents, dyes, detergents, dispersants, etc. The total amount of these additives will usually range from about 0.1 20 percent by weight, and more usually from about 05-10 weight percent. The individual additives may vary in amounts from about 0.01- weight percent of the total composition.

The compositions of this invention may be used with a wide variety of lubricating media, including oils of lubricating viscosity, as well as greases. Various base oils which find use include oils such as petroleum lubricating oil; naphthenic base, paraffin base, and mixed base; synthetic oils; alkylene polymers and alkylene oxide polymer; esters of organic and inorganic acids; aryl hydrocarbons and ethers; organic silicone compounds; etc. The base oils can be used individually or in combinations, wherever miscible or wherever made so by the use of mutual solvents.

As will be evident to those skilled in the art, the various modifications of this invention can be made or followed in the light of the foregoing disclosure and discussion without departing from the spirit or scope of the disclosure or from the scope of the following claims.

6 I claim: 1. A lubricating oil composition comprising a major amount of lubricating oil and rust inhibiting amount of a composition of the general formula wherein R is a hydrocarbyl radical of from 8 to 25 carbon atoms,

and

R is an N-heterocyclic radical composed of carbon, hy-

drogen and nitrogen.

2. A lubricating oil composition according to claim 1 wherein R is derived from pyridine and alkylpyridine.

3. A lubricating oil composition according to claim 1 wherein R is an alkenyl radical derived from alpha-olefins or an oligomer of a C -C olefin.

4. A lubricating oil composition comprising a major amount of lubricating oil and a rust inhibiting amount of a composition of the general formula wherein R is an hydrocarbyl radical of from 8 to 25 carbon atoms,

and

R is a saturated N-heterocyclic radical composed of carbon, hydrogen and nitrogen, and containing one nitrogen atom which is directly bonded to the succinyl radical.

5. A lubricating oil composition according to claim 4 wherein R is derived from pyrrolidine or piperidine.

6. A lubricating oil composition according to claim 4 wherein R is an alkenyl radical derived from alpha-ole fins or an oligomer of a C -C olefin.

References Cited 

